Inconsistent mileage per tank

[D Fresh]

I hand compute each tank in cases where I'm driving 65mph, in low winds, on flat ground, with minimal payload (eg one passenger), as a good reference. I make sure I frequently change synthetic oil and that it's the correct level.
Always MAX 20 mpg both ways at constant 65 mpg, flat ground, low winds, etc. Sometimes 19.

2) I've also tried the opposite strategy that some people advised (accelerate quickly to use boost, then cruise), with no improvement (but slightly worse mpg)

Any modifications?

I average 19-20 mpg on premium in the summer months. And that's lifted on E-rated 33"s.

If your truck is stock I feel like you apparently got yourself a mileage lemon.

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[Langwilliams]

@jblc
Me too I bitched, for 1,5 yrs, we had the same as you. This spring
when the gas went up, my wife changed her driving habits
a little. She is soft on take off & on cruise asap. We were doing 24mpg constantly this summer.
Back to winter gas. With all my other cars, from 1980 to 2000 I would lose 100km per tank, 60 miles, so it's normal.
As for why it drops, several reasons, just my thoughts/experience.
- Whatever they add in the gas(?) If they do.
- Remote start
- Wheel spin on snow/ice
- What I think most people don't think. The air is cold & therefore more resistance. This sounds a little weird I'm sure but for those
who ride. They can confirm or deny.
All I can say is when I ride & it's hot, 90F, I don't 'feel' the wind.
But when it's 40/45, man, it feels like I'm hitting a brick wall, quite a difference.

I have always wondered if one of the reasons it drops is cool/cold air packs denser an makes more power. To avoid a lean condition I wonder if the efi system has to add more fuel when it's cold out to keep the afr where it's programmed to be. My three boys are all mechanical engineers but don't deal with cars. Hell they barely check their oil.
I also read winter blend is less efficient.

 

[Frenchy]

I have always wondered if one of the reasons it drops is cool/cold air packs denser an makes more power. To avoid a lean condition I wonder if the efi system has to add more fuel when it's cold out to keep the afr where it's programmed to be. My three boys are all mechanical engineers but don't deal with cars. Hell they barely check their oil.
I also read winter blend is less efficient.

In general you do make more power when it is cold out vs hot out. I cant remember the exact equation but I think it was roughly 1% more power for every 10° F lower you went? I could be wrong on this. That said with more available power you technically do not have to use as much throttle due to having more power. Even with an older vehicle that is stock, you make a decent modification that adds some power. As long as you are being moderate with the throttle(wich is almost impossible for all of us here) mileage will most likely go up.

 

[scrubaducky]

I try not to care or notice too much but I remember when i first got my truck in july i was getting around 375-425 miles per tank. Lately I’ve noticed I get around 300-350 at most. Is is something to do with weather? I drive with adaptive cruise control almost 24/7 and only set it 3-5mph over the speed limits sometimes. WHenever i fill up i reset and it will start out showing 22-24 mpg average but then by the time im empty it’s reading 19 or so. Just curious is all.

I've noticed the same thing, 400+ estimated milage from June (when I got it) till Nov, then 300-350 since early Nov.

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